1. Field of the Invention
The present invention relates to a pointing stick, and more particularly, to a pointing stick with increased sensitivity.
2. Description of the Prior Art
A pointing stick, used for controlling the movements and position of a cursor on a computer display, is used in many types of devices, such as keyboards, mice, joysticks, and remote controls.
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a perspective view of a prior art pointing stick 10, and FIG. 2 is an operational diagram of the pointing stick 10. The pointing stick 10 includes a base 12, a rod 18, a cruciform foundation plate 20, and four strain gauges 16 set on a bottom side 22 of the cruciform foundation plate 20. The rod 18 is set perpendicular to the middle portion of the cruciform foundation plate 20. As shown in FIG. FIG. 2, the cruciform foundation plate 20 bends while be pressed from the top end of the rod 18 and, as a result, the strain gauges 16 stuck to the bottom side 22 of the cruciform foundation plate 22 deform to generate corresponding sensing signals.
As shown in FIG. 2, each strain gauge 16 includes a pressure resistor 24, a first electrode 26, and a second electrode 28. The pressure resistor 24 deforms according to the bending of the cruciform foundation plate 20, and thus offers a varying resistance. The first electrode 26 and the second electrode 28 are set on the right and the left side of the pressure resistor 24 respectively for allowing a current L to flow from the first electrode 26, through the pressure resistor 24, and to the second electrode 28. While the pressure resistor 24 is deformed horizontally, the horizontal resistance of the pressure resistor 24 varies also, leading to variation of the current L to generate corresponding sensing signals.
But the pointing stick 10 relies only on the bending of the cruciform foundation plate 20 for deforming the pressure resistor 24 to output sensing signals. Therefore, the sensitivity of the strain gauge 16 relies solely on the elasticity of the cruciform foundation plate 20, and so is not as sensitive as possible.
It is therefore the objective of the present invention to provide a pointing stick with increased sensitivity.
In accordance with the claimed invention, a pointing stick includes a substrate, an input pillar set perpendicular to the substrate, and at least one strain gauge for sensing pressure and producing pointing signals corresponding to the pressure. A portion of the strain gauge is set between the input pillar and the substrate. The strain gauge includes a first pressure resistor set on an upper surface of the substrate. A first electrode and a second electrode are electrically connected to the first pressure resistor. The first electrode and the second electrode form a loop to pass current through the first pressure resistor. The first electrode and the second electrode are separated by a gap with a predetermined distance in a pressing direction, which is perpendicular to the surface of the substrate.
It is an advantage of the present invention that the gap between the first electrode and the second electrode increases the sensitivity in the pressing direction so that the pointing stick of the present invention produces pointing signals not only according to the bend of the pointing stick itself but also according to deformation in the pressing direction.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.